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EC number: 220-011-6
CAS number: 2602-34-8
[3-(2,3-epoxypropoxy)propyl]triethoxysilane hydrolyses in the presence
of water, including atmospheric moisture, to ultimately yield 2,3-dihydroxypropoxypropylsilanetriol
and ethanol. The hydrolysis half-life is12 –36
hours at pH 7 and 25⁰C.
However the ecotoxicity studies that are available for the registered
substance were conducted at pH 8. At this pH the hydrolysis rate is
expected to be 5 to 10 times faster and it is therefore likely that,
under the static and semi-static exposure conditions of the aquatic
toxicity tests reported in the following sections, the test organisms
will have been predominately exposed to the hydrolysis products of the
The properties of ethanol have been discussed extensively in the public
literature. Ethanol is considered to be non-toxic to aquatic organisms
at the concentrations at which it would have been present in the tests
reviewed in this assessment; the short-term EC50 and LC50
values for ethanol are in excess of 1000 mg/l (OECD 2004a - SIDS
for ethanol, CAS 64-17-5).
As a consequence of the above, the environmental hazard assessments that
follow (including those for sediment and soil compartments) are based on
the assumption that any observed effects are the result of exposure to a
mixture of the registered substance,
[3-(2,3-epoxypropoxy)propyl]triethoxysilane, the intermediate hydrolysis
product [3-(2,3-epoxypropoxy)propyl)silanetriol and the ultimate silanol
hydrolysis product, 2,3-dihydroxypropoxypropylsilanetriol.
There are two characteristics of the substance that are thought to
confer toxicity to the substance: the presence of the epoxy group in the
molecular structure and the log Kow of the substance.
Hydrolysis of the substance can occur at the epoxy group and at the
alkoxy group. The hydrolysis of the epoxy group will result in an open
ring, which is less reactive and less toxic. The hydrolysis of the
alkoxy group will generate a silanetriol with a lower log Kow and
thus a less bioavailable form of the substance. The intermediate
hydrolysis product 3-(2,3-epoxypropoxy)propyl)silanetriol is expected to
be less toxic than the parent substance because even though the epoxy
ring is still present it has a lower log Kow value. Likewise,
it is expected to be more toxic than the ultimate hydrolysis product
because the epoxy ring is absent from the ultimate hydrolysis product
and it has a lower log Kow value.
Data available for structural analogue
short-term toxicity to aquatic organisms show LC50/EC50 values
to be in the range 1 to 10 mg/l. The hydrolysis product may persist in
the environment, however the log Kow values of the parent
substance and its hydrolysis products are <3. It is therefore proposed
that the substance is classified as Aquatic Chronic Category 2 according
to Regulation (EC) No. 1272/2008.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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